1. Field of the Invention
The present invention relates generally to the field of copper-coated semiconductor devices. Specifically, the invention relates to chemical-mechanical processes for polishing a copper-coated semiconductor device.
2. Description of Related Art
Some known chemical-mechanical processes for polishing a semiconductor body include forming a dielectric layer over the semi-conductor body, etching a plurality of trenches into the dielectric layer, and forming a barrier layer over the dielectric layer and the trenches. These known processes also include forming a copper seed level over the barrier layer and forming a copper level over the copper seed level, such that a portion of the copper seed layer and a portion of the copper level also are disposed in the trenches. In these known processes, the copper layer, the copper seed layer, and the barrier layer may be removed by a polishing pad, which may include a slurry composition disposed on the side of the polishing pad which contacts the various layers. Moreover, during the initial polishing, e.g., the polishing of the copper layer and the copper seed layer, these known processes rapidly may remove the copper layers by using a high selectivity copper-polishing slurry, e.g., a slurry which may rapidly remove the copper layer in order to maintain a high throughput. However, after the high selectivity slurry removes the copper layers and the barrier layer, the copper layer disposed inside the trenches also may become polished with the high selectivity copper-polishing slurry. This over-polishing of the copper layer disposed inside the trenches causes a depression of the copper layer, such that the copper layer becomes uneven, an effect which is known as dishing.
Therefore, a need has arisen for processes that overcome these and other shortcomings of the related art. A technical advantage of the present invention is that the copper layer, or copper layers, rapidly may be removed during the chemical-mechanical polishing process. Another technical advantage of the present invention is that a copper oxide inhibitor is added to the slurry composition during the polishing process, such that when the slurry composition contacts the copper layer disposed inside the trenches, oxidation of the copper layer is reduced or eliminated, which decreases dishing.
In an embodiment of the present invention, a process for polishing a semiconductor body is described. The process includes the steps of providing a semiconductor body, forming a barrier layer over at least a portion of the semiconductor body, and forming at least one layer comprising copper over at least a portion of the barrier layer. The process further includes the steps of polishing at least a portion of the at least one layer comprising copper with a first polishing slurry composition and changing the polishing slurry composition from the first slurry composition to a second polishing slurry composition. The process also includes the steps of polishing at least a portion of the layer comprising copper with the second slurry composition and polishing at least a portion of the barrier layer with the second slurry composition. Moreover, the second slurry composition comprises an effective amount of a copper oxide inhibitor to substantially inhibit copper oxide formation. The effective amount of the copper oxide inhibitor may be greater than about 0.005% by weight of the second slurry composition. Alternatively, the effective amount may be between about 0.005% and 0.03% by weight of the second slurry composition. Moreover, the second slurry composition may be different than the at least one first slurry composition.
In another embodiment of the present invention, a process- for polishing a semiconductor body is described. The process includes the steps of providing a semiconductor body, forming a dielectric layer over the semiconductor body, and etching a plurality of trenches in the dielectric layer. The process also includes the steps of forming a barrier layer over the dielectric layer and the trenches, forming a copper seed layer over the barrier layer, and forming a copper layer over at least a portion of the copper seed layer. The process further includes the steps of polishing at least a portion of the copper layer with a first polishing slurry composition and changing the polishing composition from the first slurry composition to a second polishing slurry composition. The process also includes the steps of polishing at least a portion of the copper layer with the second slurry composition and polishing at least a portion of the barrier layer with the second slurry composition. Moreover, the second slurry composition comprises an effective amount of a copper oxide inhibitor to substantially inhibit copper oxide formation. The effective amount of the copper oxide inhibitor may be greater than about 0.005% by weight of the second slurry composition. Alternatively, the effective amount may be between about 0.005% and 0.03% by weight of the second slurry composition. Moreover, the second slurry composition may be different than the at least one first slurry composition.
Other features and advantages will be apparent to persons of ordinary skill in the art in view of the following detailed description of the invention and the accompanying drawings.